The Kepler spacecraft was launched in 2009 to look for planets similar to our own by watching out for a characteristic dip in light coming from distant stars.
NASA has discovered more than 200 new planets and 10 of them are the right size and temperature to sustain life.
The latest discoveries add to the grand total of 4,034 planet candidates detected by the Kepler telescope.
The figure includes 10 that are "rocky" like Earth and which exist in their solar system's "Goldilocks zone", neither too close to their star, and therefore too hot, nor too far away and too cold for liquid water to exist.
This is the final catalogue from the spacecraft's view of the patch of sky in the Cygnus constellation.
By studying Kepler's data, scientists can determine if a planet is a massive gas giant like Jupiter or a small, rocky world like Earth.
The final Kepler catalogue will serve as the foundation for more study to determine the prevalence and demographics of planets in the galaxy, while the discovery of the two distinct planetary populations shows that about half the planets we know of in the galaxy either have no surface, or lie beneath a deep, crushing atmosphere an environment unlikely to host life.
"Are we alone? Maybe Kepler today has told us indirectly, although we need confirmation, that we are probably not alone", Mario Perez, Kepler program scientist, said at a news conference.
Kepler's findings bring up the total number of potential Earth-like exoplanets to 49.
That does not mean the planets have life, but some of the most basic requirements that life needs are there.
Kepler discovers new planets by observing the minuscule drop in brightness that occurs when a planet passes in front of its star.
"It's like finding what we thought was a single species of animal is really two different things", said Benjamin Fulton, a graduate student in astronomy who analysed the Kepler data.
According to the scientists, the most promising of the Earth-like exoplanet candidates appears to be KOI (Kepler Object of Interest) 7711 - a planet about 30 percent wider than Earth. This will in turn increase the chances of ascertaining the possibility of life on other planets. The telescope was a part of a research that had hoped to calculate the frequency of planets and especially the frequency of Earth-size planets.